a What is the theoretical yield in grams of hydrogen gas fro

a) What is the theoretical yield in grams of hydrogen gas from the reaction of 9.23 g of aluminum metal with 400 mL of 2.00 M aqueous hydrochloric acid (HCl(an))?

Solution

Part a

Moles of HCl = molarity x volume

= 0.400 L x 2 mol/L = 0.8 mol

Moles of Al = mass/molecular weight = 9.23/27 = 0.342 mol

Balanced equation:

2 Al(s) + 6 HCl(aq) = 2 AlCl3(aq) + 3 H2(g)

From the stoichiometry of the reaction

2 mol of Al reacts with = 6 mol of HCl

1 mol of Al reacts with = 3 mol of HCl

0.342 mol of Al reacts with = 3*0.342 = 1.025 mol of HCl

But we have only 0.8 mol of HCl

HCl is limiting reactant

Theoretical yield of H2 = 3 mol H2 x 0.8 mol HCl/6 mol HCl

= 0.4 mol H2

Part b

Net ionic reaction

2Al + 6 H+ + 6Cl- = 2Al3+ + 6Cl- + 3H2

2Al + 6 H+ = 2Al3+ + 3H2